The invention relates to a device for recirculating exhaust gases in an internal combustion engine.
EP 0 128 299 A1, for example, has taught that additional gas streams are introduced into the intake passage of an internal combustion engine behind a throttle valve to form a mixture with the intake air. The flow of the additional gas stream is regulated through a second throttle valve in the passage for the additional gas stream. In different embodiments of the known system either fresh air or recycled exhaust gas is used as additional gas. The temperature of the additional gas stream at the point of introduction is very important to the perfect operation of the system.
The invention is addressed to the problem of improving an apparatus for the recycling of exhaust gases in an internal combustion engine of the kind described above, such that optimum temperature conditions can be achieved at the point of introduction of the recycled exhaust gas.
The device according to the invention for the recycling of exhaust gas in an internal combustion engine is an advantageous improvement of the generic system, since an amount of recycled exhaust gas that is optimized, especially with regard to temperature, can be introduced into the exhaust passage of the internal combustion engine behind a throttle valve in the direction of flow. For this purpose a valve is inserted into the exhaust gas recycling passage, which admits exhaust gas and/or fresh air in a given quantity ratio, and thus produces a controllable air/exhaust gas mixture for introduction into the intake passage. The fresh air can advantageously be taken from an air filter in the intake tract of the internal combustion engine.
If a cyclically controlled valve is used the quantity ratio can be set advantageously by the cycling ratio, the mixture that is advantageous in each case being controlled by the cyclical addition of air and/or exhaust gas. The cyclical ratio of the cycled valve can in this case be chosen such that the content of the exhaust gas in the air/exhaust gas mixture ranges, for example, from 20% to 40%, the fresh air in one selected embodiment having a temperature of about 60xc2x0 C. and the exhaust gas a temperature of about 222xc2x0 C.
By appropriate adaptation to the temperature conditions at the motor, an especially short cold-start phase can be achieved in a motor vehicle with an internal combustion engine. For example, in the case of a mixture ratio of 4:1 (exhaust gas:air) in the supply line and the above-mentioned initial temperatures, a recycled mixture temperature of about 190xc2x0 C. results at the point of entry into the intake passage; this corresponds to a temperature reduction of 15%.
In the case of a mixture ratio of 3:2 the temperature is about 157.5xc2x0 C. at a recycled exhaust gas content of 30%; this corresponds in the embodiment approximately to a temperature reduction of 29%. At a mixture ratio of 2:3 the temperature is about 125xc2x0 C. at a recycled exhaust gas content of 20%; this corresponds to a temperature reduction of about 44%.
In one advantageous embodiment of the device of the invention a cooling device for the recycled exhaust gas is present ahead of the cycled valve in the direction of flow, and is connected to a cooling circuit for the internal combustion engine.
Additional advantageous embodiments will be described hereinafter of the. These and additional features of preferred embodiments of the invention will be found not only in the claims but also in the description and the drawings, the individual features being applicable individually or severally in the form of subcombinations in the embodiment of the invention and in other fields and may represent advantageous as well as independently patentable embodiments, for which protection is hereby claimed.